Presently, direct current (DC) or induction electromotive machines are generally used in diesel/electric-based locomotives, in mining vehicles and other off-highway vehicles, in certain marine vessels and aircraft, and in stationary applications (e.g., drilling applications, wind turbine drive train, etc.). The machines may be used in various operational contexts, including traction, auxiliary equipment, such as blowers or cooling equipment, and electrical power generating equipment.
Although these machines have proven through the years to be the workhorses of the industry, they sometimes suffer from various drawbacks. For example, in the case of traction motors, such motors tend to be relatively heavy, and inefficient in terms of electro-mechanical energy conversion. The capability of these machines is important not only from a fuel savings point of view but also from size, weight, cost, transient capability, cooling system, failure rate, etc. Moreover, any incremental weight of the traction motors tends to increase the transient forces on the truck (in a rail vehicle) and the road/track.
In the case of power generating equipment, DC or induction electromotive machines are typically in the form of a salient pole synchronous generator. Such generators commonly use an exciter winding in the rotor and may be energized through slip rings. The slips rings are subject to electro-mechanical wear and tear and may need burdensome and costly maintenance. Moreover, the volumetric spacing for vehicular applications (e.g., a locomotive) may have to be increased to accommodate the spacing requirements of electrical generating systems that use slip rings and exciter windings. In view of the foregoing considerations, it is desirable to provide an improved electromotive machine that avoids or reduces the drawbacks discussed above.